This invention relates to displacement sensing and guide systems, with particular application to machinery or processes which operate on materials in the shape of a continuous sheet or web and which require that the materials be introduced into and moved through a machine or a process without variance, either laterally or angularly from a predetermined position.
In the textile industry, the processes of cutting, printing, dyeing, or tufting continuous sheet fabrics or webs, or sewing one fabric over another fabric, require that the webs be properly aligned in the process. Furthermore, the alignment must be maintained despite varied widths along the length of the web. The webs are often very light or in insufficient tension to permit the direct use of any mechanical sensors, which requires either that the mechanical sensors measure a non-representative variable, such as the edge of a carpet backing sheet rather than the edge of the tufted pile of a tufted carpet, or that pressure or photoelectric sensors by used.
While the prior art discloses means for sensing deviations of moving webs from a desired path, most of these sensing means are incapable of directly measuring displacement of the edge of the web, or if the sensing means is photoelectric or pressure means capable of measuring displacement of an edge of the moving web, the sensing means requires sophisticated adjustment and it not readily adjustable for varying applications. Thus, the capability of a particular machine or process may be limited by the need for complicated adjustments whenever the width or desired displacement of the fabric, pile or web changes.
Since the design and arrangements of manufacturing equipment used in the textile industry is rarely static in the face of developing technologies, the means for sensing deviations of continuous webs from desired paths must be adapted to new configurations of processing machinery. The more the design of the sensing means must be specially designed for particular existing machines or processes, the less adaptable it is to the expected changes in machine configurations dictated by new processes.
The elaborate means of direct sensing by photoelectricity and fluid pressure usually require an investment in expensive components. The methods of indirect mechanical or electrical sensing require the measurements to be translated into useful indications by complex circuitry which also adds to their expense.
The result of these problems is that much of the present art in displacement sensing and guide means is expensive, difficult to maintain and to adjust the new uses, and, through its lack of adaptability, limits its users to existing technology. Furthermore, the extent to which the present art fails to satisfy the need for reliable and accurate displacement sensing and guide means emphasizes the need for improvement in this area.